The present invention relates to a guiding and sealing unit for a mono-tube shock absorber rod and to an annular sealing assembly incorporated within.
Hydraulic shock absorbers of the mono-tube type, extensively used in the automotive and other industries, are intended to work under relatively high hydraulic pressures, in average about 20 bars, with peaks which may reach 100 bars. In view of such high working pressures, the sealing of the pressurized oil contained in the shock absorber, acts against the reciprocating motion of the piston body.
The sealing of pressurized oil contained in the shock absorber body contrasts in application to the reciprocating motion of the piston in the body itself, and the guiding of the shock absorber rod are made by means of a guiding and sealing unit having a bushing thoroughly engaged by the rod, wherein the bushing is then fluid-tightly mounted within the body of the shock absorber, and a sealing assembly carried by the bushing, of the type described in German utility model patent application DE8201327U.
This sealing assembly of the prior art contemplates numerous elements to be mounted separately, and is thus relatively cumbersome and complex to be assembled. The situation is made additionally worse because other component elements are needed for correct operation of the shock absorber, e.g. a static seal between shock absorber body and bushing, and a limit stop element for the piston, which allows a “smooth” stop, without sudden impacts which could produce undesired noises and, in the severest cases, possible damage. Such a limit stop element is an additional, but necessary element, which is very difficult to mount and which, above all, increases dimensions in axial sense.
European patent application EP-A-06425875 discloses a sealing assembly for shock absorber rods and a guiding unit therein which the static seal is integrated with the sealing assembly provided with the dynamic sealing lip or lips towards the shock absorber rod. However, such a solution does not solve the assembly problem of the limit stop element for the piston, and may be relatively expensive to be produced, because the “static” part of the seal is produced with the same high performance elastomeric mix which is used to produce the sealing lip.
It is the object of the present invention to provide a guiding and sealing unit for a rod of a mono-tube shock absorber and a sealing assembly therein, which are free from the drawbacks of the prior art and which, in particular, are suitable for application on shock absorbers of the mono-tube type, which allow to drastically simplify the assembly of the limit stop element of the piston and which allows to reduce the length and the weight of the shock absorber maintaining the same working stroke of the piston, all this preserving the assembly ease of the unit known from EP-A-06425875. It is a further object of the invention to provide a guiding and sealing unit and a sealing assembly for shock absorber rods which are also cost-effective to produce.